On April 30th, I confirmed that access to https://foo.netlify.com/ was redirected to http://foo.netlify.app/ (foo is a tentative name, but it didn’t depend on the site).
My service relied on site assets on netlify and was getting mixed content errors.
So I rewrote the link from .com to .app and dealt with it.
But now, https://foo.netlify.com/ redirects to https://foo.netlify.app/.
I think this was a problem with netlify.